Electronic device

ABSTRACT

A method for manufacturing an electronic device by placing within a die a first lead with an element placement pad, a second lead, and an electronic element placed on the element placement pad. The electronic element, the element placement pad, a part of the first lead, and a part of the second lead are sealed in a package by injecting a sealing resin in the die from a position on a longer side of the package, with the position being offset toward one shorter side thereof. The first lead is bent in an S shape, with a bending depth being at least as large as the thickness of the first lead. A thickness of the resin on a non-device side of the element placement pad is smaller than the bending depth.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resin-sealed surface mount electronicdevice.

2. Description of the Prior Art

With reductions in the size of electronic equipment, there has been anincrease in the use of surface mount semiconductor devices, such asdiodes and transistors, and the size of these devices also is beingreduced.

FIG. 3 shows the general construction of a surface mount diode of thepast, FIG. 3(A) being a plan view thereof, and FIG. 3(B) being across-section view as seen from the direction indicated by the arrowsalong the line II—II in FIG. 3(A).

The electronic device 100 of FIG. 3 has a first external lead 110, whichhas a electronic element placement pad (die pad) 111 for placement of anelectronic element, and a second external lead 120, which is disposed ata distance from the element placement pad 111. A semiconductor element130 is placed on the element placement pad 111. A bonding wire 150 makesa connection between an external connection terminal of thesemiconductor element 130 and the second external lead 120. Thesemiconductor element 130, the electronic element placement pad 111, theinner lead part of the first external lead 110, the inner lead part ofthe second external lead 120, and the bonding wire 150 are sealed by asealing resin 140. As shown in this drawing, the first external lead 110and the second external lead 120 are bent in an S shape, with one end ofthe leads 110 and 120 exposed to the outside of the sealing resin 140,so as to form outer lead parts. The lower surfaces of the outer leadsextend in a direction that is substantially parallel to the bottomsurface 141 of the sealing resin 140, and are substantially on the sameplane as the bottom surface 141 of the sealing resin 140.

The above-noted electronic device is manufactured by first punching outand bending a thin metal sheet to the appropriate shape to form a leadframe, onto which the semiconductor device is placed. Then, after makingthe prescribed connections, the device is sealed using sealing resin.The sealing with the sealing resin 140 is done within a die of theprescribed shape, so as to include the electronic element placement pad111, the inner lead part of the first external lead 110, and the innerlead part of the second external lead 120, resin being injected via aresin injection port 190, indicated by the double-dot-dash line, on oneof the shorter sides of the device.

The dimensions of a usual resin sealed electronic device of the pastwere approximately a vertical dimension (X-axis dimension L_(X) in FIG.3) of 1.3 mm, a horizontal dimension (Y-axis dimension L_(Y) in FIG. 3)of 0.8 mm, and a height (Z-axis dimension H in FIG. 3) of 0.7 mm.

Because the thickness of the lead frame used in an electronic device ofthe past was 0.1 mm or greater, however, it was difficult to achieve asurface mount electronic device with a resin package having all of thevertical, horizontal, and height dimensions smaller than approximately 1mm, including resin-sealed semiconductor devices making use of asemiconductor substrate.

Because the thickness of the lead frame is 0.1 mm or greater, thespacing between the element placement pad 111 of the first external lead110 and the second external lead 120 grows to over 0.2 mm by theformation of the lead. Because of the relationship between suchparameters as the lead bending depth, the associated thickness of theresin at the bottom of the element placement pad 111 that is requiredtherefor, the lead length required for bending, and the establishment ofa flat surface for placement of an element, in the case of diodes inparticular, it was not possible to achieve a vertical length of lessthan 1.0 mm.

As electronic devices became smaller, because of the delicate bendingshape of the bent parts 112 and 122 near the bottom surface of thesealing resin of the external leads, there was a tendency toward suchproblems as insufficiencies in the adhesion and filling in of sealingresin, the strength of the lead itself, and the adhesive strengthbetween the lead and the sealing resin, and poor adhesion and filling inof solder used for mounting, and it was difficult to achieve anelectronic component that provided improvements in these deficiencies.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anelectronic device that solves the problems of the limitation in sizereduction of surface mount resin sealed electronic devices in the past,and to enable the achievement of an electronic device having a resinpackage with vertical, horizontal, and height dimensions that are allbelow 1 mm.

It is another object of the present invention to provide a resin sealedsurface mount electronic device that, even with a reduction in size ofthe electronic device, provides good filling in of sealing resin to thebent parts near the bottom surface of the sealing resin of the externalleads, good adhesion strength between the leads and the sealing resin,and good strength in the leads themselves, and further providing goodadhesion and filling in of solder when the device is mounted.

To achieve the above-noted object, the present invention has thefollowing constitution.

Specifically, a first aspect of an electronic device according to thepresent invention has an electronic element, a first external lead withan element placement pad having a thickness t of less than 0.1 mm, and asecond external lead that is disposed at a distance from the above-notedelement placement pad, wherein the electronic element, the elementplacement pad, part of the first external lead, and part of the secondexternal lead are sealed with a sealing resin, the first external leadbeing bent in an S shape, the bending depth d thereof being at least aslarge as the thickness t of the first external lead, and the thickness Tof the resin on the non-device side of the element placement pad beingsmaller than the bending depth d.

In the first aspect of an electronic device of the present invention,the first external lead thickness t, the relationship of this thicknesst to the bending depth d, and the relationship between the sealing resinthickness T at the bottom of the element placement pad and the bendingdepth d are established. By doing this, it is possible to limit theheight of the electronic device, and to achieve the flat area requiredin the element placement pad. Additionally, because the spacing betweenthe element placement pad and the second external lead can be madeshort, it is possible to reduce the dimension in the vertical direction.

In the configuration of the above-noted first aspect of the presentinvention, it is preferable that the spacing between the elementplacement pad and the second external lead be made no greater than 0.12mm. Using this preferable configuration, it is possible to make afurther reduction in the vertical-direction dimension of the electronicdevice.

In the above-noted configuration, it is preferable that the outervertical, horizontal, and height dimensions of the sealing resin all beno greater than 1.0 mm. Using this preferable configuration, it ispossible to achieve a compact electronic device that was not possible toachieve in the past, thereby contributing to the reduction in size ofelectronic equipment.

In the first aspect of the present invention, it is preferable that thewidth of the inner lead parts of the first and second external leadswithin the sealing resin be of a substantially uniform width and notbroaden beyond the exposed part. Using this preferable configuration, itis possible to obtain a compact electronic device having a width(Y-direction dimension) that does not become large. The effect ofreducing the package size is particularly significant in the case in ofan electronic device having three or more terminals.

In the above-noted configuration, it is preferable that the thickness ofthe electronic element be substantially the same as the thickness t ofthe first external lead. Using this preferable configuration, it ispossible to make the height of the bonding wire the same as that of thechip.

In the above-noted first aspect of the present invention, it ispreferable that the sealing resin be injected from a position on eitherof the longer sides that is offset towards a shorter side. By providinga sealing resin injection port at such a position, the injected resinextends well into the package die, without a tendency toward theformation of eddies and/or accumulations, thereby preventing problemswith insufficient sealing resin filling.

In the first aspect of the present invention, it is preferable that thebending radius R of outer surface of the bent part of the first externallead in the region of the sealing resin bottom surface be at least 0.05mm, but no greater than the lead thickness t. Using this preferableconfiguration, it is possible not only to prevent both constriction ofmaterial and lead bending during lead formation, but also to achieveflexibility of the frame with respect to stress that is applied indownstream processes.

In the first aspect of the present invention, it is preferable that thesealing resin includes filler that has a particle diameter that is nogreater than half the bending depth d of the lead. This preferredconfiguration facilitates the filling in of sealing resin and filler atthe lower surface of the bent lead, thereby maintaining sufficientformation strength.

The second aspect of an electronic device according to the presentinvention has an electronic element, a first external lead with anelement placement pad having a thickness t of less than 0.1 mm, and asecond external lead that is disposed at a distance from the above-notedelement placement pad, wherein the electronic element, the elementplacement pad, part of the first external lead, and part of the secondexternal lead are sealed with a sealing resin, the first external leadand second external lead being bent at the bottom surface of the sealingresin, extending in a direction that is substantially parallel to thebottom surface of the sealing resin and being exposed. A depression isformed in the bottom surface part of the bent part of the first externallead and the second external lead, at which depression the thickness ofthe lead is reduced, the bottom surfaces of the depressions of the firstand second external leads and the bottom surface of the sealing resinbeing formed so as to be higher than the lowermost surfaces of the partsof the first and second external leads which extend outside.

According to the above-noted second aspect of the present invention, byproviding a depression in the bottom surfaces of the bent parts of thefirst and second external leads, good filling of sealing resin isachieved in the region of the bent parts, thereby improving the adhesionstrength between the leads and the sealing resin, another effect beingan improvement in the strength of the leads themselves. Because thebottom surfaces of the depressions and the bottom surface of the sealingresin are formed so as to be higher than the lowermost surfaces of theparts of the first and second external leads which extend outside, goodadhesion and filling of solder is achieved when mounting the device to acircuit board.

In the second aspect of the present invention, it is preferable that thedepression be formed within the projected boundaries of the sealingresin as seen from above. By adopting this preferred configuration, thedesign of the shape in the region of the depression of the resin dieused for resin sealing is facilitated, and it is easy to prevent leakageof sealing resin from the area surrounding the depression when resinsealing is done. Additionally, because the formation of the depressionis accompanied by a reduction in the thickness of the lead, by formingthe depression within the above-noted region, it is possible tocompensate for the loss of strength caused by this accompanyingreduction in lead thickness by means of sealing resin in the surroundingarea. Additionally, because it is possible to form the lowermostsurfaces of the first and second external leads within the region thatis projected from above the sealing resin, it is possible to achieve asufficient contact surface area between the circuit board and the leads,even if the exposed parts of the first and second external leads areshortened. It is therefore possible to reduce the mounting surface areaof the electronic component, thereby contributing to a reduction in sizeof the overall electrical equipment.

In the second aspect of the present invention, it is preferable that asealing resin escape part be formed at the side bottom part of thesealing resin, and that bottom edge position of this escape part besubstantially the same as the forming position of the depression, andthat the distances between these positions and the border with theabove-noted region projected from above the sealing resin both be nogreater than the thickness of the lead. By forming a sealing resinescape part at the at the bottom side part of the sealing resin, removalfrom the resin die after resin sealing is facilitated. By making theformation position of the depression substantially the same as thebottom edge position of the escape part, it is possible to form thelowermost surfaces of the first and second external leads within aregion projected from above the sealing resin. As a result, even if theparts of the first and second external leads that are exposed from thesealing resin are made short, it is possible to achieve a sufficientcontact surface area between the circuit board and the leads. Thisenables a reduction in the size of the mounting surface area of theelectronic component, therefore contributing to the reduction in size ofthe electronic equipment. Additionally, because the distances from theborder of the region projected from above the sealing resin to thebottom edge position of the escape part and the formation position ofthe depression are both no greater than the lead thickness, it ispossible to optimize the reduction in the device size, the lead bendingangle, and the sealing resin thickness at the bottom of the elementplacement pad, while achieving a sufficient element placement pad.

In the second aspect of the present invention, it is preferable that thelower surfaces of the first and second external leads have a flat partthat protrudes beyond the depression, within the projected boundaries ofthe sealing resin as seen from above. By doing this, the flat partsformed on the lower surfaces of the first and second external leadsserve as the contact surfaces with the circuit board, these contactsurface being inside the region projected from above the sealing resin,so that it is possible to shorten the parts of the first and secondexternal leads that are exposed from the sealing resin, thereby enablinga reduction in the mounting surface area, and contributing to thereduction in size of the electronic equipment.

In the second aspect of the present invention, it is preferable that thebottom surface of the sealing resin be higher than the lowermost surfaceof the part of the first and second external leads that extend outsideby 0.001 to 0.02 mm. By doing this, it is possible to achieve a goodbalance between the above-noted effect of the depression and a reductionin the size of the electronic component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing that shows the general construction of an example ofthe first embodiment of an electronic device according to the presentinvention, (A) being a plan view thereof, and (B) being a cross-sectionview thereof, as seen from the direction indicated by the arrows alongthe line I—I shown in (A).

FIG. 2 is a drawing that shows the general construction of an example ofthe second embodiment of an electronic device according to the presentinvention, (A) being a cross-section view thereof, and (B) being abottom view thereof.

FIG. 3 is a drawing which shows the general construction of an exampleof a electronic device of the past, (A) being a plan view thereof, and(B) being a cross-section view thereof, as seen from the directionindicated by the arrows along the line II—II shown in (A).

FIG. 4 is a cross-sectional drawing that shows the general constructionof an example of the first embodiment of an electronic device accordingto the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1 shows the general construction of the first embodiment of anelectronic device according to the present invention, (A) being a planview thereof, and (B) being a cross-section view thereof, in thedirection indicated by the arrows along the line I—I shown in (A).

As shown in this drawing, an electronic device 1 according to thisembodiment has a first external lead 10, which has an element placementpad (die pad) 11, and a second external lead 20, which is disposed at adistance from the element placement pad 11. A semiconductor electronicelement 30 is mounted to the element placement pad 11 by means of diebonding or the like. Bonding wires 50 make a connection between anexternal connection terminal of the electronic element 30 and the secondexternal lead 20. The semiconductor electronic element 30, the elementplacement pad 11, the inner lead part of the first external lead 10, theinner lead part of the second external lead 20, and the bonding wire 50are sealed by a sealing resin 40.

As shown in FIG. 1, the first external lead 10 and the second externallead 20 are bent in an S shape (substantially a step shape), with oneend of the leads 10 and 20 exposed to the outside of the sealing resin40, extending in a direction that is substantially parallel to thebottom surface of the sealing resin 40 so as to form outer lead partsrespectively.

In this case, the thickness t of the first external lead 10 is less than0.1 mm. If this thickness t is larger than this, it is not possible toachieve a compact electronic device. In a case in which the thickness ofthe inner lead part within the sealing resin and the thickness of theouter lead part differ (for example, in the case in which the outer leadpart is plated with solder), the thickness t refers to the thickness ofthe inner lead part.

If the bending depth of the first external lead 10 shown in FIG. 1 is d,it is necessary that the thickness t of the lead satisfy the conditiond≧t. If the thickness of the sealing resin on the non-element side ofthe element placement pad 11 is T, it is necessary that the conditionT<d be satisfied. By satisfying these relational conditions, it ispossible to make the vertical-direction (X-axis direction) dimensionL_(X) and the height-direction (Z-axis direction) dimension H small.

In the above-noted embodiment of an electronic device according to thisembodiment, it is preferable that the widths of the inner lead parts ofthe first external lead and second external leads within the sealingresin be of substantially uniform width and not broaden beyond thewidths of the exposed (outer) lead parts. In the past, because thickleads were bent within the resin, externally applied stress caused bycutting of the lead frame or common connection parts during themanufacturing process risked pulled-out leads and damage to the sealingresin. To prevent these problems, therefore, the lead ends of theexternal leads within the sealing resin were widened (refer to FIG.3(A)). With this embodiment of the present invention, however, by makingthe thickness of the leads less than 0.1 mm, it is possible to establisha mechanical balance, thereby enabling the shape (width) of the externallead to be made substantially uniform, without widening in its innerlead part. By doing this, it is possible to reduce thehorizontal-direction (Y-axis direction) dimension L_(Y).

To achieve a balance in strength within the sealed package, it ispreferable that the inner lead part thickness t be made substantiallythe same as the semiconductor element 30 thickness.

The position of the sealing resin injection port 90 in this embodiment,as shown by the double-dot-dash line in FIG. 1, and as shown in FIG. 4,is preferably on a longer side of the package, offset from the centerthereof towards one of the shorter sides, avoiding the bonding wires 50,with sealing resin being injected therethrough in the direction shown bythe arrow 93 in FIG. 1, in order to prevent the bonding wires 50 fromtoppling by injection pressure of the sealing resin acting on the sidesurfaces of the bonding wires 50 directly. By making the resin packagesmall, it would be difficult as done in the past to provide a resininjection port on a shorter side of the package. Additionally, becausethe spacing between the inner wall of the resin die, shown in FIG. 4 asupper die 91 and lower die 92, and the inner lead becomes narrow, itwould be difficult to cause resin to sufficiently fill in under theinner lead. For this reason, by injecting sealing resin, as noted above,from a longer side at a position that is offset toward one of theshorter sides of the package, the resin fills into the die smoothly,thereby preventing problems with insufficient resin filling.

It is preferable that the bending radii R at the outer surfaces of thebent part of the inner lead part of the first external lead 10 near thebottom surface of the sealing resin be at least 0.05 mm and no greaterthan the thickness t of the lead. Specifically, in FIG. 1(B), it ispreferable that the bending radii R₁₁ and R₁₂ of the outer surfaces ofthe bent part 12 of the first external lead 10 in the region of thebottom surface of the sealing resin be at least 0.05 mm and no greaterthan the thickness t of the lead. Additionally, it is preferable thatthe bending radii R₁₃ and R₁₄ of the outer surfaces of the bent partnear the element placement pad 11 of the inner lead part of the firstexternal lead 10 also satisfy the same type of condition. It is furtherpreferable that the outer surface bending radii R₂₁, and R₂₂ of the bentpart 22 of the second external lead 20 near the bottom surface of thesealing resin be at least 0.05 mm and no greater than the thickness ofthe second external lead. Additionally, it is preferable that thebending radii R₂₃ and R₂₄ of the outer surfaces of the bent part nearerto the wire bonding end of the inner lead part of the second externallead 20 satisfy the above-noted type of condition. If these conditionsare satisfied, it is possible to prevent constriction of material andbending of leads when the leads are formed, as well as to achieveflexibility of the frame with respect to stress that is applied indownstream processes.

A more specific form of the above-noted embodiment is described below.

Using a lead frame having a thickness t of 0.08 mm, with a bending depthd of the first external lead 10 of 0.12 mm and a resin thickness T of0.11 mm at the bottom of the element placement pad 11, it was possibleto place an semiconductor element 30 having a chip size of 0.3 mmsquare, the spacing L₁ between the element placement pad 11 and thesecond external lead 20 being 0.11 mm. All the bending radii R₁₁, R₁₂,R₁₃, R₁₄, R₂₁, R₂₂, R₂₃, and R₂₄ on the outer surfaces of the bent partsof the inner lead parts were made 0.05 to 0.1 mm. Under theseconditions, the resin package vertical dimension (X-axis directionlength in FIG. 1) L_(X), horizontal dimension (Y-axis direction lengthin FIG. 1) L_(Y), and height (Z-axis direction length in FIG. 1) H were1 mm, 0.5 mm, and 0.5 mm, respectively, this representing an extremelycompact package.

An example of a method for manufacturing the above-noted electronicdevice is described below.

First, a flat lead frame having a thickness of 0.08 mm was punched outand formed with a 0.12 mm depth bend. An element placement pad wasformed on the first external lead, and a wire bonding region was formedon the second external lead. Next, the element placement pad was placedon a heater, and die bonding of a semiconductor element was performedwhile applying heat thereto. Then, the external connection terminal ofthe semiconductor element was wired to one end of the external lead withbonding wire. After that, the element placement pad, the semiconductorelement, and one end of the external leads were sealed using a sealingresin. The resin injection port used to do this was provided on one ofthe longer sides of the package, offset from the center toward a shorterside. The particle diameter of the filler that was included in the resinwas selected as approximately 50 μm or smaller, which was not greaterthan half of the bending depth d of the leads, so as to improve thefilling in of the sealing resin around the bottom parts of the leads.

With a lead thickness t of 0.08 mm, if the lead bending depth d was madeshallower than the lead thickness t, it was found that the balancebetween the thickness of the resin that holds the lead at the bottompart of the lead and the lead strength is disturbed, resulting in atendency for the package to crack.

It was further discovered that, with a lead thickness t of 0.08 mm, ifthe lead bending depth d was made larger than 0.13 mm in an attempt toshorten the vertical-direction (X-axis direction) dimension L_(X), itwas difficult to achieve a flat surface on the element placement pad forthe purpose of die bonding, making it difficult to make an electronicdevice any smaller. Thus, it was found to be preferable to establish thedepth d as no greater than 0.13 mm under above condition.

Next, solder plating was done on the outer lead part of the firstexternal lead, having an element placement pad, and the outer lead partof the second external lead. Although this can result in a case in whichthe external lead thickness after solder plating exceeds 0.1 mm, thispresents no problem. Finally, the lead frame was cut at a length of 0.2mm from the outer edge of the resin package, thereby completing thedevice.

Second Embodiment

FIG. 2 shows the general construction of the second embodiment of anelectronic device according to the present invention, (A) being across-section view thereof, and (B) being a bottom view thereof.

Elements in the second embodiment that have the same function as thosein the first embodiment have been assigned the same reference numerals,and will not be described in detail herein.

In the second embodiment of an electronic device according to thisembodiment, depressions 13 and 23, respectively, are formed on the lowersurfaces of the bent parts 12 and 22 of the first external lead 10 andthe second external lead 20, near the bottom surface 41 of the sealingresin 40. The depressions 13 and 23 are formed by coining or the like,and the thicknesses of the leads 10 and 20 near the parts at which thedepressions 13 and 23 are formed are thinner than the thicknesses of theinner lead parts. The lower surfaces of the depressions 13 and 23 andthe bottom surface 41 of the sealing resin 40 are formed so as to behigher than the lowermost surface 14 of the outer lead part of the firstexternal lead 10 and the lowermost surface 24 of the outer lead part ofthe second external lead 20.

It is preferable that the height of the lower surface of the depressions13 and 23 and the height of the bottom surface 41 of the sealing resin40 be made 0.001 to 0.02 mm higher than the lowermost surfaces 14 and 24of the outer lead parts, and further preferable that the increase inheight be no greater than 0.01 mm. By making the height of the lowersurface of the depressions 13 and 23 and the height of the bottomsurface 41 of the sealing resin 40 in the above mentioned range, goodadhesion and filling of solder to the outer lead parts is achieved whenmounting the device to a circuit board. If the height of the bottomsurface 41 of the sealing resin 40 is made greater than the above-notedupper limit, the resin layer on the bottom side of the element placementpad 11 becomes thin, so that an attempt to achieve the required resinthickness results in a higher resin package. If the lower surfaces ofthe depressions 13 and 23 are made higher than the above-noted range,the part of the lead at which the depression is formed will becomeexcessively thin, resulting in a loss of lead strength. From thestandpoint of lead strength, the thickness of the lead at the part atwhich the depression is formed is preferably no less than 90% of thethickness of the inner lead part. While there is no need for the lowersurface of the depressions 13 and 23 to be formed in the same plane asthe bottom surface 41 of the sealing resin 40, forming these on the sameplane is preferable, as it facilitates the design of the resin die.

By providing the depressions 13 and 23 in this manner on bent parts 12and 22 of the leads, the angle that the lower lead surface makes withrespect to the sealing resin bottom surface 41 at the lead bent parts 12and 22 near the bottom surface 41 of the sealing resin 40, that is, theangle of rise of the inner leads with respect to the sealing resinbottom surface 41, becomes large. For this reason, the thin part of thesealing resin under the inner lead parts in the region of the bottomsurface 41 of the sealing resin is reduced. The result is that sealingresin filling in around the lead bent parts 12 and 22 is good, and theforming of the sealing resin bottom surface is stabilized in the areasurrounding the bent parts 11 and 22. There is therefore an improvementin the adhesion strength between the leads and the sealing resin, inaddition to an improvement in the strength of the leads themselves.

It is preferable that the depressions 13 and 23 be formed inside of theouter peripheral edge of the resin package, as viewed from either thetop or the bottom. By adopting this configuration, if the design is madesuch that the surface of the die used for resin sealing that will be thebottom surface 41 of the sealing resin 40 is on the same plane as thedepressions 13 and 23, it is possible easily to prevent the leakage ofresin from the area surrounding the depressions when resin is injectedinto the die. Because the formation of the depressions is accompanied bya reduction in the lead thickness, by forming the depressions within theabove-noted region, it is possible to support the entire part in whichthe thickness is reduced with sealing resin, and to prevent a loss oflead strength. Additionally, because it is possible to form thelowermost surfaces of the first and second external leads within theprojected boundaries of the sealing resin as seen from above, i.e.within the peripheral edges of the resin package, it is possible toachieve a sufficient contact surface area between the circuit board andthe first and second external leads, even if the exposed parts of thefirst and second external leads are shortened. It is therefore possibleto reduce the mounting surface area of the electronic component, therebycontributing to a reduction in size of the overall electrical equipment.

In general, to facilitate removal from the die used for resin sealingafter injection of the sealing resin, an escape part with predeterminedinclination angle with respect to the abutted surfaces of the top andbottom parts of the die is provided in the die. In this embodiment ofthe present invention, it is preferable, as shown in FIG. 2(B), to formthe bottom edge position 43 of the escape part 42, which has an angle ofθ and is formed on the bottom of the exposed-lead side of the sealingresin, so that the bottom edge position 43 is substantially the sameposition as the forming edges 15 and 25 of the depressions 13 and 23. Bydoing this, the depressions 13 and 23 are formed inside of the outerperipheral edge of the resin package, thereby achieving the above-notedeffect.

It is preferable that the distance L₂ from the outer peripheral edge ofthe resin package to the bottom edge position 43 of the escape part 42and to the forming edges 15 and 25 of the depressions 13 and 23 be nogreater than the lead thickness. If the distance L₂ is greater than theabove-noted limit, it not possible to achieve a sufficient region foruse as the element placement pad 11, and an attempt to achieve asufficiently sized element placement pad 11 will result in an increasein the size of the resin package, an increase in the bending angle ofthe leads, or the need to make the thickness T of the layer of resinunder the element placement pad 11 thin.

The outer lead parts can be plated after sealing with resin, and theaccompanying increase in thickness does not cause a problem.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, all changes that come within the meaning and range ofequivalency of the claims are intended to be embraced therein.

What is claimed is:
 1. A method for manufacturing an electronic devicecomprising: placing within a die a first lead with an element placementpad having a thickness t of less than 0.1 mm, a second lead that isdisposed at a distance from said element placement pad, and anelectronic element placed on said element placement pad; and sealing ina package said electronic element, said element placement pad, a part ofsaid first lead, and a part of said second lead by injecting a sealingresin, in a direction substantially parallel to a surface of saidelement placement pad, in the die from a position on a longer side ofthe package, said position being offset toward one shorter side thereof;wherein a portion of said first lead is bent in a substantially S shape,the S shape portion is substantially confined within the package, afirst end of the S shape extends to the element placement pad to mountthe electronic element and a portion of a second end of the S shapeextends partially outside the package, a bending depth d being at leastas large as the thickness t of said first lead, and a thickness T ofsaid resin on a non-device side of said element placement pad is smallerthan said bending depth d.
 2. The method according to claim 1, whereinthe spacing between said element placement pad and said second lead isno greater than 0.12 mm.
 3. The method according to claim 1, wherein thevertical, horizontal and height outer dimensions of said sealing resinare each no greater than 1.0 mm.
 4. The method according to claim 1,wherein widths of inner lead parts of said first and second leads withinsaid sealing resin are substantially uniform.
 5. The method according toclaim 1, wherein the thickness of said electronic element issubstantially the same as the thickness t of said first lead.
 6. Themethod according to claim 1, wherein a bending radius R on an outersurface of a bent part of said first lead near a bottom surface of saidsealing resin is at least 0.05 mm and is no greater than the leadthickness t.
 7. The method according to claim 1, wherein the sealingresin contains a filler, whose particle diameter is not greater thanhalf the bending depth d of the said first lead.